Retinal dysplasia is a term applied to retinal malformation which includes, rosettes and gliosis seen in eyes of human infants and of animals. This change can be induced by a variety of conditions which affect the immature retina including viral infections. Herpesvirus is a widespread infection of human and animals and can cause congenital anomalies. Feline sarcoma virus is known to cause tumors in kittens. The effect of viruses on immature tissue vary from latent infection, inflammation, malformation and tumor formation. This study proposes to follow the retinal changes induced by canine herpes virus in germ free puppies and by feline sarcoma virus in kittens. Studies will be conducted by light and electronmicroscopy and will help to elucidate the sequence of events on the tissue and cellular levels of the retina, with special attention to malformation and neoplastic changes.